US890776A - Damper for the upper harmonics of alternating electric currents. - Google Patents

Description

No. 890,776. Y PATENTED JUNE 16, 1908. M. LEBLANC. DAMPER FCR THEUPPER IiARMONICS 0E ALTBRNATING ELECTRIC CURRENTS.

PATBNTED JUNE 16', 1908.

No. 890,776. M. LBBLANG.

DAMPBR F011 THB UPPER HARMONIcs 0F -ALTBRNATING ELECTRIC GURRENTS.

APPLIOATIOI FILED APB. 28, 1905.

2 sHnBTs-s'HBBT 2.

i UNITEDSTATES"PATENTOEEIOE MAURICE LEBLANC, or PARIS, FRANCE, vAssIciNOR To WESTINGEOUSE ELECTRIC AND' MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA.

DAMPER FOR THE UPPER HARMoNIcs oF ALTEn-NATING ELECTRIC' cimmiii'rs.v

Application-A 28,

v ments in Dampers for-thdUpperfHarmonics of Alternatin the' following is a specification. f @My -'nventio n hasreferenCG-Q improve; L ments inthe transmissi'OIlfO electrical energy and-fitconsists in an apparatus for preventing' an undue oi' dangerous resonant rise of potenf l. tial-infalterna'ting currentv transmission sys-A temsdueto-'the ca acity ofthejliiie and-the 1f5 self inductionof t 'e generators and motors installed ini-the system.

Iris a Weii known manina the aieriaang currents generated by any of the"4 ordinary generators are not of the simple sinusoidal 2O type, but are accompaniedby currents Aof the' e oddl'upper harmonica-so that in any Ordinar alternating current ifit be analyzed, there will be found in addition yto 4 the fundamental sinusoidal 'current also currents 'of the third,

ifth,seventh, etc., upper harmonics.

' 'Inpractice it has beenfound `that the sys-y l'tem of distributionis rarely, if'e'ver', resonant to the frequency' of thefunda'mental current, but that resonance to one`or the `other of the fupper harmonics frequently occurs andthat "for diifer'entloads the `resonance maychange from -One harmonic vto another. In conse'- .finance of such resonance the potential rises y frequently to a highand dangerous point and 3*5 mayfbecome destructive lof the machines.

if jItis easy, with the present knowledge of {hej-art, to builfd alternating machines, by properly designingtheir pole pieces 'and b properwinding', 'so lthat such machines wi l rnonic. By my invention'I am able to effectively\ 'suppress 'the resonant riseof potential duf tothe ninth and higher harmonics whichiS-p'eciicaton of Letters Patent. l

Electric Currents,\ of which lmatter of mechanical construction, to use ratenteanme 1c, 190e.-

1905. s enaiNo. 257,397. f

mental frequency. I do by supplying to onejoi' more of the alternating current genof veryhigh resistance, preferably laced near .the air gap, taki care that suc high lowresistance circuits. While I- prefer,'as a highresistance circuits-in the form of. squirrel cages on the magnetic poles of the alternating current machine, Imay reach-the same'resultby placing high external resistancesin circuitwiththe circuits of the machine. To 'prevent some circu'itf onl the machine from screening the highresistanceharmonic-damper circuit, iflthe two be in inductive prox- Imity,-1 may 'place an impedance coil therein frequency which it isdesired tosuppress'. I

are not to actas screen`s,`to an'armature of thedirect'current ty e, and I drive the varmature at a speed 'w 'cli causes the `circuits to act as an obstructionfor the high frequency harmonic currents, but to assist the low frequency currents. vIn the accompanyin apparatus that may e used in the practice 'O my invention are illustrated as follows:

Fi ure 1 is a cross-section of an alternator provided with means for suppressing the rise of po'tential; Fig 2 is a like view of an alternator providedwith means for sup ressing means for preventin the hunting ofthe machine; Fig. 3 is a li e view of theessential parts of an induction motor provided with means for reventing a resonant rise of potenillustrating tioii may be practiced. j f Like numerals and` letters of reference 1ndicate like parts in all figures of drawing..

Referring to Fig. l, which represents a part is assed through its coils3, in the ordinary well known manner. The ringzi is Intended in thewindings ofwbih the alternating curerators or-motorsuse'd inthe system, circuits .fresistancejcircuits sli-al not be screened by may, however, connect the circuits, which the resonant rise of potential and a so withtial, and iUs. 4, 5, 6, P[and 8, are diagrams.

different ways in which my invento represent an ordlarystationary armature,

I which hasl an inducta'nce which is-low for thev alternating currents of vnormalfrequency and which is 'high forfthe currents of harmomc "drawingfv which forms a part of this s ec` cation some of the 10o A of van'alternator, 2,2, etc. are the-rotating.v iield poles energizedby direct current which rents are generated which go to line.l On the polar extensions ofthe field poles are shown sectional squirrel cages composed vof conductors 5 of high resistance, which pass through the polar extensions vfrom side to side and are at their ends united by strips or cheek plates 6 of metal, in'the usual manner of vconstructing squirrel cages. lnstead-of using a separate air of cheek plates for each sectional squirre -cage, .two complete rings niay be used, which would thus serve as the cheek plates for all polepieces; such construction-is-indicated in' Patent No. 529,272, granted jointly to M. Hutin and myself. The

field structure must be laminated in order to prevent the generation of parasitic currents. 'llie squirrel-cage rods must be of exceptionally high resistance, and they may for this urpose be made-of thin copper or preferab y of German silver, and they should pers of harmonics or harmonic dampers.

An essentialr condition for obtaining the desired result is that the 'fiuX produced by the harmbnics may intersect the high resist- 'ance harmonic damper circuit without traversmg anyv circuit of low resistance closed upon itself; Such low resistance circuits closed upon themselves would act as a shield 'against the high speed fluxes developed by the harmonics and; the. action of which upon the' damper circuits is necessary in order to obtain the result aimed at. For the same reason the harmonic damper circuits should never he applied to massive iron cores, they should always be a plied to laminated cores, which cannot be tlhe seat of Foucault currents capable of demagnetizingl the cores perceptibly. Now the use of low resistance circuits closed upon themselves on the field poles of alternators and motors is of great advantage for the suppression of speed oscillations of such machines, as is explained in the United States patent granted to M. Hutin and myself $529,272, dated November 13th, 1894, and such circuits are now largely used for suppressing 'the hunting of alternating current machines. Therefore, in order to combine in one machine lthe benefits of anti-hunting (called deadener circuits) with the harmonic dampers hereinbefore described, the dampers must not be arranged on the same pole pieces with the deadeners; and such arrangementl have indicated in Fig. 2. ln this alternator, which has ei ht poles, two adjlacent pole pieces are rovi ed .with sectiona squirrel cages of higi resistance 5, 5; the two next pole pieces are prol vided with low resistance anti-hunting sectional squirrel cages 7, 7, and so forth, so that none of the high resistance harmonic dampers are screened by the low resistance deadeners.

In Fig. 3 my invention is shown as applied to an induction motor in which 8 represents supposed t'o be the field structure receiving the rotor and 10 the stator, the latter being in its windings the currents from the line. If

the rotor or'secondary member had a low resistance squirrel cage winding my invention would not be ap )licable to it, since the low iesistance squirrel cage would act as a screen to any harm onic dampers of high resistance that could be applied. This induction motor therefore is provided with a coil winding 9, 9, located in slots and connected to three collector rings 11, 12, 18, placed on the shaft of the machine, and on these rings bear brushes as indicated in Fig. 4, which are connected to inductance coils 14, 15, 16 outside of the machine. In the bottoms of the slots in which the windings 9 are placed are, located the high resistance harmonic damper conductors 5, connected at each endby a cheek plate or ring 6. From the electrical point of view it would be preferable to place the harmonie damper 'conductors above the windings 9, so as to be closer to the air gap; but this construction would involve difficulties from a purely mechanical view. of the armature were closed upon themselves within the machine, they wouldl also serve as screens to the harmonic dampers, and this is the reason why the armatureI windings are closed outside the machine as indicated in Fig. 4. The coefiicient ofself induction of these coils 14, 15, 16, must be sufficiently low to permit the passage of currents of the slip frequency, which means the frequency of 2 at the utmost, but sufficiently large to offer a great impedance to the passage of currents of a fre uency greater than thenormalfre uencyoft elinecurrents. In other words, t ese self induction coils exterior to the machine but in the circuits of the armature will themselves act in a manner to suppress the resonant rise of otential without acting as a screen to the amper circuits proper. The presence of these self-induction coilsin ordinary induction motors diminishes the power factor and the maximum torque of the motor for a given voltage. This difficulty is overcome by the arrangement shown in Fig. 5, Where the brushes bearing upon the collector rings. 11, 12, 13,4 are connected with the commutator of an armature 17, of a direct current type, the field for whicli'may be asimple laminated iron ring 18, and the armature 17 may be mounted on the shaft of the induction motor, or may be eared to it.

If the windings 9 develop in the saine a rotary field which, with reference to vthe brushes, has a speed equal to l the frequenc of these currents.

. armature by the harmonics .on the line have,

- the rtor of the armature 17` such a will behave as condensers for the useful curcurrents. Thisv arrangement will by itself .act to a certain extent to-suppress the rise of reducingl either the power factor or the maximum torqueof the machine for a given lvol- 'spect may bel obtained by placing between whichis free ofselfinduction.

Viu'lig. 6 in which ,casetliewinding of the is providedwith the high resistance harmonic ings will prevent the windings 17 from acting thereto I have indicated selfr induction coils 14, 15, 16, in the circuits proceeding from the 4no other currents.

rect current type winding 17 is also supposed .motor and which reach the armature of the the stator circuits.

\ tween the brushes 19, 21 2 N 0W it is known that the rotor turns slower than the field the circuits comprised- `between its brushesbehaye as if theyhad self induction; while when the rotor turns faster than the field the circuits comprised f b'etWeennthe brushes behave like condensers. The useful currentsl which traverse the armature of the induction direct :current type ave. a very "low `frequency, the frequency of the slip while the currents developed in the.. induction motor on the con-trar avery-hi h-frequency. Under theseV con itions it will be easy to glve t o f spec that .the circuits'with which it is connected rents and as'self inductionsfor the 'harmonic potential of the harmonicswithout operating as a screen-to the action of the big resistance'harmonicdamper circuits, an without tage. A further improvement in this reea'ch pair of brushes 19, 20;- 20, 21 and 21, 19, like very-high resistancesl 1" which have no 'selfin'duction 4.and the like improvement can also be lmade in the' arrangementV yshown in Fig.- l4 by'shunting'each self induction lcoil 14, 15, 16,l lyhav ike very high resistance Another efficient arrangement isiindicated direct current armature 'type 17is"s1-1pposed to be placeddirectly upon thfe rotor ,-8, which dampers; and in this case the brushes 19, 20, 21, are connected with the stator windings With this arrange'- ment the self inductions of the'stator Windas a'screen to the fluxes Vproduced-across the rotor by the passageof harmonic currents in The Asame [arrangement is also indicated in Fig. 7, butgin additionA brushes 19, 20 and 21, respectively. The presence of these self-induction coils does not sensibly affect the power or the power factor of thegmachine, since the circuits comprised between the brushes would behave like condensers, for the useful' ci'rents and for 'Inithe arrangement shown in v8 the dito be placed dlrectly on the rotor 18, and the 14, 15, 16, are placed beself inductionl coils 1,-20 and 21,19,

respectively.

From the foregoing it will .understood that in all induction machinesthe s'tat'orlnfdxeach other and the secondaries'recei've almost the whole flu-x generatedwby the' primary Winding. IIf thereforethe secondary .circuits are provided with high resistanees Whicha're free of self induct1on,loutside of the machine,

From the foregoing it will ibe-understood that my invention is` applicable lto all kinds of alternating current generatorsy and motors,

including rotary converters, except to induction machines of the kind in Whichrthe'se'condary member is constituted by a-low resistance squirrel cage. l

rotor windings are generally,,veryfclosetoV I have attained excellent results by usingv an alternating current machine in which I have converted the ordinary inducing cir-. cuitsjinto high-resistance harmonic-damper f circuits by adding external resistancecoils to s each inducing circuit, which resistance coils each have an ohmic resistance of 75 times los that of eachinducing circuit, as it originally f y stood.

Havingnw fully described my invention I claim and desire t'o secure by'L'etter's Patent; f

1. An alternating current machine `provided with an unscreened veryhigh-resist' ance harmonic-damper circuit, substantially l` o 2. An alternating current machine having a harmonic-damper circuit made of a resistance sufficiently high to effectively suppress upper harmonics, as 'herein defined, and 4a Winding in inductive proximitythereto of a.

'self-induction which -is made low forithe lowfrequency currents flowing therein but high for the currents of upper harmonic frequency, whereby the winding. does not actas a screen for the dam er, substantially as described.

ltipola-r .alternating current Inalchine having certain poles supplied with `high resistance harmonic damper circuits A 3.Amu

and other. poles supplied with low resistance anti-hunting circuits, Whereb the antihunting circuits do not screen the armonicdamper circuits, substantially as described@ 4.-An alternating current machine su pied with a circuit of a resistance su'iciently -gh to effectively su press the upperA harmonies, vas herein de ined, substantially a's described.

5. An alternating current machine supeffectively suppress the upper harmonics, es

plied with a squirrel-cage circuii'J made of a herein defined, substantially as described. 10 resistance sniiiciently high to effectively supl ln testimony whereof l have signed my press the u per harmonics, as herein defined7 naine to this slwciicuvticn. 5 substantial yA as described.\ MAURICE LEBLANC.

6. A n alternating current machine sup- Witnesses: plied with a squirrel-cage circuit vnear the l ALBERT Dame,

air gap 0f a resistance su'lliciently high to l F. T. CHAPMAN.

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